12 Canis Majoris

Variable star in the constellation Canis Major 250px A visual band light curve for HK Canis Majoris (2020) J2000 Canis Major 06 47 01.48353 −21 00 55.4517 +6.07 B7 II/III or B5 V −0.159 0.004 SX Ari +16.4 2.5 −14.568 +5.778 4.6155 0.0543 −0.81 4.8 2.73 537 15830 60 commas −0.37 4.23 65 2.18045 d 134 HK CMa 12 CMa −20°1576 817 49333 32504 2509 172318 8884 12+CMa 12 Canis Majoris is a variable star located about 707 light years away from the Sun in the southern constellation of Canis Major. It has the variable star designation HK Canis Majoris; 12 Canis Majoris is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07. It is moving away from the Earth with a heliocentric radial velocity of +16 km/s. This is the brightest star in the vicinity of the open cluster NGC 2287, although it is probably not a member based on its proper motion. The Bayer designation ρ Canis Majoris/Rho Canis Majoris has been applied to this star in the past, but this is now rarely seen. Perhaps the best-known use was by Charles Messier when describing the cluster Messier 41: "cluster of stars below Sirius, near Rho Canis Majoris". This star has a stellar classification of B7 II/III, matching the spectrum of a B-type star intermediate between a giant and bright giant. (Cidale et al. (2007) show a class of B5 V, which would indicate it is instead a B-type main-sequence star.) It is a magnetic Bp star of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the atmosphere. Holger Pedersen and Bjarne Thomsen discovered that 12 Canis Majoris is a variable star, in 1977. It was given its variable star designation in 1981. Samus et al. (2017) classify it as an SX Arietis variable that varies in brightness by about 0.05 magnitudes over a period of 2.18045 days. It has 4.8 times the mass of the Sun and 2.73 times the Sun's radius. The star is radiating 537 times the Sun's luminosity from its photosphere at an effective temperature of commas 15830 K. References Adam Len Imaging the Messier Objects Remotely from Your Laptop Springer 2018-04-04 978-3-319-65385-3 https://books.google.com/books?id=7nNUDwAAQBAJ&q=%2522rho%2520canis%2520majoris%2522&pg=PA202 2025-05-21 Gontcharov G. A. Dependence of kinematics on the age of stars in the solar neighborhood Astronomy Letters December 2012 38 12 771–782 1063-7737 1562-6873 10.1134/S1063773712120031 2012AstL...38..771G 1606.08814 free Pedersen H. Thomsen B. Spectrum and photometric variability of He-weak and He-strong stars Astronomy and Astrophysics, Suppl. Ser. October 1977 30 11–25 1977A&AS...30...11P https://articles.adsabs.harvard.edu/pdf/1977A%26AS...30...11P 1 January 2025 2022MNRAS.513.1429S MOBSTER - VI. The crucial influence of rotation on the radio magnetospheres of hot stars Shultz M. E. Owocki S. P. Ud-Doula A. Biswas A. Bohlender D. Chandra P. Das B. David-Uraz A. Khalack V. Kochukhov O. Landstreet J. D. Leto P. Monin D. Neiner C. Rivinius Th Wade G. A. Monthly Notices of the Royal Astronomical Society 2022 513 1 1429 10.1093/mnras/stac136 free 2201.05512 Kholopov P. N. Samus N. N. Kukarkina N. P. Medvedeva G. I. Perova N. B. 65th Name-List of Variable Stars Information Bulletin on Variable Stars February 1981 1921 1 1981IBVS.1921....1K https://ibvs.konkoly.hu/pub/ibvs/1901/1921.pdf 1 January 2025 Bernhard Klaus Hũmmerich Stefan Paunzen Ernst New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data Monthly Notices of the Royal Astronomical Society 17 February 2020 493 3 3293–3330 10.1093/mnras/staa462 free 2020MNRAS.493.3293B 2002.06435 12 CMa April 30, 2019 2926942116843379968 XHIP: An extended hipparcos compilation Anderson E. Francis Ch. Astronomy Letters . 38 5 331 2012 2012AstL...38..331A 1108.4971 10.1134/S1063773712050015 119257644 1 Shulyak D. Paladini C. Causi G. Li Perraut K. Kochukhov O. Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities Monthly Notices of the Royal Astronomical Society 443 2 1629 2014 2014MNRAS.443.1629S 1406.6093 10.1093/mnras/stu1259 free 96452769 . Seismology and activity of the F type star HD 49933 Mosser B. Bouchy F. Catala C. Michel E. Samadi R. Thévenin F. Eggenberger P. Sosnowska D. Moutou C. Baglin A. 1 Astronomy and Astrophysics 431 L13–L16 February 2005 2 10.1051/0004-6361:200500003 . 2005A&A...431L..13M astro-ph/0501459 18412104 Multicolor photometry of the open cluster NGC 2287 1 Feinstein A. Cabrera A. L. Claria J. J. International Astronomical Union, Reunion Astronomica Regional Latinoamericana, 1st, Santiago, Chile, Jan. 16-21, 1978 Chile, Universidad Departamento de Astronomia, Publicaciones 3 146–149 1979 1979rarl.conf..146F . Axial rotation in NGC 2287 Levato H. Garcia B. Astrophysical Letters 24 3 161–164 1984 1984ApL....24..161L . Houk Nancy Smith-Moore M. Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars 4 Ann Arbor 1978 Dept. of Astronomy, University of Michigan 1988mcts.book.....H . Stratification of helium in the photospheres of the helium-weak stars HD 28843 and HD 49333 Farthmann M. Dreizler S. Heber U. Hunger K. 1 Astronomy and Astrophysics 291 919–927 November 1994 1994A&A...291..919F . Abundances determined using Si ii and Si iii in B-type stars: Evidence for stratification Bailey J. D. Landstreet J. D. Astronomy & Astrophysics . 551 A30 2013 1301.3050 10.1051/0004-6361/201220671 2013A&A...551A..30B 59291051 1 Samus N. N. Kazarovets E. V. Durlevich O. V. Kireeva N. N. Pastukhova E. N. General Catalogue of Variable Stars 5.1 Astronomy Reports 2017 61 1 80–88 10.1134/S1063772917010085 2017ARep...61...80S 125853869 . Chemically peculiar stars and their temperature calibration 1 Netopil M. Paunzen E. Maitzen H. M. North P. Hubrig S. Astronomy and Astrophysics 491 2 545–554 November 2008 10.1051/0004-6361:200810325 . 2008A&A...491..545N 0809.5131 14084961 Fundamental parameters of He-weak and He-strong stars Cidale L. S. Arias M. L. Torres A. F. Zorec J. Frémat Y. Cruzado A. 1 Astronomy and Astrophysics 468 1 263–272 June 2007 10.1051/0004-6361:20066454 . 2007A&A...468..263C 0705.0541 14143604 Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others Wagman Morton The McDonald & Woodward Publishing Company Blacksburg, VA 2003 460 978-0-939923-78-6 2003lslm.book.....W Category:B-type giants Category:B-type bright giants Category:B-type main-sequence stars Category:Helium-weak stars Category:SX Arietis variables Category:Canis Major Category:Durchmusterung objects Canis Majoris, 12 049333 032504 2509 Canis Majoris, HK